Switch device



July 17, 1951 L. D. laoYcEr SWITCH DEVICE Original Filed Oct. 27, 1944INVEN TOR.

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E C VI m D. a m D 5 R n 2 A Y G B F 2 1 O D lz 7 4 5 s 4 e 4 4 2 31. 2 u3 ..m W in wf .7 5 4 l G F 3 Patented July 17, 1951 SWITCH DEVICELeonard D. Boyce, Kirkwood, Mo., assigner to Carter CarburetorCorporation, St. Louis, Mo.,

. a corporation Original application October ,27, 1944, Serial No.

560,656. Divided and this application December 17, 1948, Serial No.65,900

1 Claim.

This invention relates to transmission control mechanisms for automotiveengines and consists particularly in novel means for preventingoperation of the so-called over-drive throw-out when the vehicle istravelling at such a rate of speed that the consequent increased speedof the engine would endanger the parts thereof.

This application is a division of my copending application, Serial No.560,656, filed October 27, 1944, now abandoned, which is a continuationin part of an application Serial No. 340,819, filed June 15, 1940, nowabandoned.

Wherefthe transmission gearing for an automobile is provided with a,so-called over-drive, which is engaged automatically when the vehicle istravelling at higher than a predetermined speed, it is desirable toprovide for greater power and faster acceleration particularly in caseof an emergency as lwhen the vehicle, though travelling in over-drive,must suddenly be speeded to pass another car. When the operator movesthe throttle to fully open position in order to accelerate the vehicle,the automatic transmission is likely to shift to a more powerful gearratio, as from fourth or direct drive to third gear. It has been foundthat with such arrangement, where the vehicle is travelling at 45 milesan hour or faster, the transmission cannot be safely returned to thirdgear, as above described, due to the consequent excessive engine speed.Considerable power and some time is required to bring the engine up tothe necessary speed and, in fact, this may be impossible when the car isalready travelling at high speeds.

It has been suggested that this problem may be solved by providing forkick-down of the gearing ratio when the throttle Valve is substantiallywide open while preventing such kickdown in case the engine istravelling above a certain predetermined speed.

It is the main object of the present invention to provide a novelthrottle and suction operated switch device for use with such a gearingarrangement.

A more detailed object is to provide such a switch device having areciprocating suction piston provided with stabilizing means.

Fig. l is a diagrammatic view showing portions of an automobile engineincluding the carburetor and transmission with the invention appliedthereto.

Fig. 2 is an enlarged View of a portion of the carburetor shown in Fig.1 but taken at 90 thereto, the over-drive throw-out switch beingsectioned on line 2-2 of Fig. 1 for clearer illustration.

2 A Fig. 3 is a sectional view of the switch as in Fig. 2 but showingthe switch contacts engaged. Fig. 4 is a view similar to Fig. 3 butshowing the switch contacts rendered ineffective to` complete theoverdrive throw-out circuit.

Fig. 1 shows at I0 a portion of an internal combustion engine oftheautomotive type includ.- ing an intake manifold I I mounting acarburetor generally indicated at I2. A clutch and change speedtransmission gearing of any suitable form are mounted, respectively, inhousings I3 and I4 secured to the rear portion of the engine. Thetransmission is provided with over-drive :mechanism located within ahousing I5 forming a rearward extension on housing I4 and directlyconnected to the usual propeller shaft I6 for driving the rear axle. Asolenoid device II is mounted on the side of the over-drive housing I5and, when energized, functions in a known manner to throw out theover-drive or, in other Words, return the transmission gearing fromover-drive position to third or the next higher and more powerful gearratio. l

Solenoid I'I is controlled by an electrical circuit including storagebattery I8 having one terminal grounded, as at I9, and a switch devicegenerally indicated at 20 mounted upon the carburetor IZ. The storagebattery and switch are connected to solenoid I'I, respectively, by leads2| and 22, the latter being connected to an insulated terminal 23forming one of the contacts of switch 20 (Figs. 2, 3 and 4). Thedetailed construction of the solenoid as well as the over-drive andother parts of the transmission do not in themselves, constitute thepresent invention and are not illustrated. For convenience, I have showna manual shift lever 24 for shifting the transmission gearing throughthe usual reverse, and first, second, and third forward gears, but thisshifting may be effected by other suitable means. As is lwell known, theover-drive portion of the transmission is automatically engagedresponsive to predetermined output speed of the transmission mechanismor, in other words, wheel speed.

Heretofore, the control circuit for the overdrive throw-out solenoid I'Ihas been controlled solely by a throttle actuated switch so thatwhenever the throttle pedal 25 is fully depressed, this solenoid isenergized for automatically reshifting from over-drive to third gear. Inthe present invention, I incorporate an additional suction control forthe solenoid switch Which renders the switch ineffective to energize thesolenoid under predetermined suction conditions. This switch includes anangular body portion 30, the legs thereof being hollowed as at 3l and32. Hollow leg 3| forms a cylinder for slidably receiving a cup-shapedpiston 33 normally urged downwardly by a coiled spring 34 seated againstan inner surface of the piston and a shoulder 35 formed in the upperportion of the cylinder. A passage 3E connects the cylinder above piston33 to the interior of the carburetor barrel or mixture conduitpreferably at the throat of venturi 31 (Fig. 2). A port 39 connects thecylinder below the piston to atmosphere and this port may lead to theair inlet horn of the carburetor so that the air will be drawn throughthe usual air cleaner (not shown). Secured to the undersurface of piston33 is an angular spring clip 31', the projecting leg of which carries ametallic ball or enlargement 38 adjacent, but normally slightly spacedfrom the inner extremity of switch contact 23 (Fig. 2). The body 30 ofthe switch device is grounded through the carburetor, intake manifold,and engine block, but piston 33 is formed of insulating material toprevent shorting of switch contact 23. The piston has a pair of legs,one being shown at 33', depending on opposite sides of terminal bushing23 and cooperating with the inwardly Aprojecting portion thereof toprevent rotation of `the piston and extension 31 from the operativeposition shown. Legs 33' also fix the lower or normal position ofthepiston and extension.

The other hollowed arm of the switch body slidably receives a hollowedswitch actuating plunger 40 and a collar 4| formed on a pin 42 slidablyreceived within plunger 40 and extending longitudinally through a screwcap 43 secured to the end of this leg of the switch body. I

Collar 4| is normally urged outwardly against cap 43 by a coiled spring44 and plunger 40 is similarly urged outwardly by a coiled spring 45whereby a yielding one-way connection is formed between the switchplunger and pin to three pounds greater than the compressive strength ofthe spring 45. This results in a one to three pound limitation on thepressure which may be applied to the contact point 38. These contactpoints are frequently made of silver and would be deformed by theexcessive pressure which might be exerted by the pressure of the driversfoot on the accelerator. The spring arrangement is such as to resistinward movement of the control member 40 after the throttle has beenopened far enough to contact the switch points and move together thecoils of spring 45. Thereafter, a conscious effort of the operator willbe required to compress spring 44 and telescope rod 42 into member 40.

Pivotally mounted in the carburetor mixture conduit posterior to venturi31 is a butterfly throttle valve which may be manually operated in theusual manner by means of a suitable arm 52 (shown in part) rigidlyattached to throttle shaft 5I. Also formed on throttle arm 52 is anextension 53 positioned to engage stop 54 to fix the wide open positionof the throttle valve, and a second arm 55 carrying an adjustable screw56, the end 56 of which engages the stop 54 to x the closed position ofthe throttle valve. A third arm 51 formed rigidly with throttle crank 52is positioned to engage switch contact pin 42 when the throttle valve issubstantially fully opened (Figs. 3 and 4l)y to 4 urge this pin andswitch contacting plunger 4P) inwardly against enlargement 38 carried bypiston 33 and to urge this enlargement in the direction of switchcontact 23. Spring 34 is adjusted so as to maintain piston 33 in itslowermost position, as in Fig. 3, whenever the suction at the throat ofventuri 31 is less than approximately 1.8 inches of mercury, whichcorresponds with a vehicle speed of approximately 45 miles an hour. Whenthis degree of suction is exceeded at the throat of the carburetorventuri, that is, when the vehicle is travelling in excess cf 45 milesan hour, piston 33 will be lifted against spring 34 into engagement withshoulder 58 formed in a wall of cylinder 3| so as to raise enlargementor ball 38 and prevent contact of switch terminal 23 thereby (Fig. 4).Thus, when the predetermined venturi suction is exceeded, the switch isautomatically rendered inefective to energize the over-drive throw-outsolenoid I1. Whenever the suction in venturi 31 is less thanapproximately 1.8 inches of mercury, ball 33 will be positioned so thatwhen plunger 40 is forced inwardly due to the throttle valve beingVfully opened, switch contact 23 will be grounded through thisenlargement, plunger 40 and the switch body so as to complete thesolenoid control circuit and cause reshifting of the transmissionmechanism from over-drive to third gear. v

By means of the illustrated structure, the overdrive, which isautomatically engaged at a wheel speed of, say 35 miles an hour, may bethrown out whenever the driver demands maximum power and fully opens thethrottle valve, but at vehicle speeds in excess of 45 miles an hour,when it would be unsafe to reshift the gearing from over-drive to ahigher ratio of engine to wheel speed, such reshifting is automaticallyprevented. Thus, it is possible to use a higher third gear ratio thanheretofore so as to attain better power and acceleration at the lowerspeeds.

In the operation of the device shown in Figures 1 to 4, the suctionmaintained in the venturi 31 acts on the piston 33 to hold it in upwardposition against the pressure of the spring 34 whenever the gear speedand throttle position exceed predetermined values. When the piston 33 isin the position shown in Figure 4, the opening of the throttle will notresult in closing of the circuit through the contact member 38, as thefriction created by the pressure exerted on. contact member 38 and theinsulation surrounding the terminal 23 by the end of the member 40 is sogreat that the spring 34 cannot shift the piston 33 downwardly.

When the throttle is opened with the piston 33 in the position shown inFigure 3, contact is made through the member 33, and the gear shiftmechanism is operated. As long as the operator holds his foot on thethrottle, the friction due to the pressure on the member 38 will preventany suction build-up in the venturi from withdrawing member 38 frombetween members 23 and 40 to break the circuit and cause reshifting ofthe transmission. This is a desirable feature, because the shock ofreshifting the transmission from a lower gear to a higher gear would betoo great when the gear speed is in excess of the predeterminedpermissible limit, for instance, 45 miles per hour.

For the reasons outlined above, the transmission control preventsautomatic shifting of gears to a lower gear ratio when the venturisuction exceeds a predetermined amount and prevents Backs? automaticshifting to a higher ratoas long as the throttle is held insubstantially open position. In accelerating the car to its maximumspeed, the operator must release the accelerator pedal sufficiently towithdraw the end of plunger 40 from contact with the member 38 in orderto cause a step-up in the gear ratio.

The invention may be modied in various respects as will occur to thoseskilled in the art and the exclusive use of all suoli modifications ascome within the scope of the appended claim is contemplated.

I claim:

A device of the class described including a cylinder, a pressureresponsive piston therein, a switch terminal element projecting intosaid cylinder, and an electrical conductor carried medially by saidpiston for cooperation with said element, portions of said pistonstraddling and extending beyond said conductor and said terminal elementand cooperating with said element to prevent rotation of said piston andalso cooperatm ing with an end Wall of said chamber so as to x theoperative relationship of said conductor and terminal element in theextreme position of said piston.

LEONARD D. BOYCE.

REFERENCES CITED The following references are of record in the lle ofthis patent:

UNITED STATES PATENTS

